Implement "pinned" mode in ash.

ash/common/wm/workspace/workspace_layout_manager.cc

Index: ash/common/wm/workspace/workspace_layout_manager.cc
diff --git a/ash/common/wm/workspace/workspace_layout_manager.cc b/ash/common/wm/workspace/workspace_layout_manager.cc
index 7304c365400127795ec93771b85c74c9447bf77f..8c8caabd3e17cae908683cf6b5ed6736dc55122e 100644
--- a/ash/common/wm/workspace/workspace_layout_manager.cc
+++ b/ash/common/wm/workspace/workspace_layout_manager.cc
@@ -33,7 +33,8 @@ WorkspaceLayoutManager::WorkspaceLayoutManager(
       shell_(window_->GetShell()),
       delegate_(std::move(delegate)),
       work_area_in_parent_(wm::GetDisplayWorkAreaBounds(window_)),
-      is_fullscreen_(wm::GetWindowForFullscreenMode(window) != nullptr) {
+      is_fullscreen_(wm::GetWindowForFullscreenMode(window) != nullptr),
+      is_pinned_(WmShell::Get()->IsPinned()) {
   shell_->AddActivationObserver(this);
   root_window_->AddObserver(this);
   root_window_controller_->AddObserver(this);
@@ -44,8 +45,11 @@ WorkspaceLayoutManager::WorkspaceLayoutManager(
 WorkspaceLayoutManager::~WorkspaceLayoutManager() {
   if (root_window_)
     root_window_->RemoveObserver(this);
-  for (WmWindow* window : windows_)
+  for (WmWindow* window : windows_) {
+    wm::WindowState* window_state = window->GetWindowState();
+    window_state->RemoveObserver(this);
     window->RemoveObserver(this);
+  }
   root_window_->GetRootWindowController()->RemoveObserver(this);
   shell_->RemoveActivationObserver(this);
 }
@@ -173,20 +177,17 @@ void WorkspaceLayoutManager::OnFullscreenStateChanged(bool is_fullscreen) {
   if (is_fullscreen_ == is_fullscreen)
     return;
 
+  bool was_always_on_top_allowed = !is_fullscreen_ && !is_pinned_;
   is_fullscreen_ = is_fullscreen;
-  WmWindow* fullscreen_window =
-      is_fullscreen ? wm::GetWindowForFullscreenMode(window_) : nullptr;
-  // Changing always on top state may change window's parent. Iterate on a copy
-  // of |windows_| to avoid invalidating an iterator. Since both workspace and
-  // always_on_top containers' layouts are managed by this class all the
-  // appropriate windows will be included in the iteration.
-  WindowSet windows(windows_);
-  for (auto window : windows) {
-    wm::WindowState* window_state = window->GetWindowState();
-    if (is_fullscreen)
-      window_state->DisableAlwaysOnTop(fullscreen_window);
-    else
-      window_state->RestoreAlwaysOnTop();
+  bool is_always_on_top_allowed = !is_fullscreen_ && !is_pinned_;
+  if (is_always_on_top_allowed != was_always_on_top_allowed) {
+    // In this pass, if is_always_on_top_allowed is false, then fullscreen
+    // window should be found. It is because; the situation only happens
+    // when was_always_on_top_allowed is true, so (is_fullscreen, is_pinned)
+    // is changed from (false, false) to (true, false).
+    UpdateAlwaysOnTop(is_always_on_top_allowed
+                          ? nullptr
+                          : wm::GetWindowForFullscreenMode(window_));
   }
 }
 
@@ -284,6 +285,22 @@ void WorkspaceLayoutManager::OnPostWindowStateTypeChange(
 }
 
 //////////////////////////////////////////////////////////////////////////////
+// WorkspaceLayoutManager, ShellObserver implementation:
+
+void WorkspaceLayoutManager::OnPinnedStateChanged(WmWindow* pinned_window) {
+  bool is_pinned = pinned_window->GetWindowState()->IsPinned();
+  if (is_pinned_ == is_pinned)
+    return;
+
+  bool was_always_on_top_allowed = !is_fullscreen_ && !is_pinned_;
+  is_pinned_ = is_pinned;
+  bool is_always_on_top_allowed = !is_fullscreen_ && !is_pinned_;
+  if (is_always_on_top_allowed != was_always_on_top_allowed) {
+    UpdateAlwaysOnTop(is_always_on_top_allowed ? nullptr : pinned_window);
+  }
+}
+
+//////////////////////////////////////////////////////////////////////////////
 // WorkspaceLayoutManager, private:
 
 void WorkspaceLayoutManager::AdjustAllWindowsBoundsForWorkAreaChange(
@@ -329,4 +346,19 @@ void WorkspaceLayoutManager::UpdateFullscreenState() {
   }
 }
 
+void WorkspaceLayoutManager::UpdateAlwaysOnTop(WmWindow* window_on_top) {
+  // Changing always on top state may change window's parent. Iterate on a copy
+  // of |windows_| to avoid invalidating an iterator. Since both workspace and
+  // always_on_top containers' layouts are managed by this class all the
+  // appropriate windows will be included in the iteration.
+  WindowSet windows(windows_);
+  for (auto window : windows) {
+    wm::WindowState* window_state = window->GetWindowState();
+    if (window_on_top)
+      window_state->DisableAlwaysOnTop(window_on_top);
+    else
+      window_state->RestoreAlwaysOnTop();
+  }
+}
+
 }  // namespace ash